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            <h2 class="title" style="clear: both"><a id="tupleswithkeycreators"></a>
		Using Tuples with Key Creators
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      <p>
    Key creators were used in prior examples to extract index keys
	from value objects. The keys were returned as deserialized key
	objects, since the serial format was used for keys. In this
	example, the tuple format is used for keys and the key creators
	return keys by writing information to a tuple. The differences
	between this example and the prior example are:
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            <p>
            The 
            <a class="ulink" href="../../java/com/sleepycat/bind/serial/TupleSerialKeyCreator.html" target="_top">TupleSerialKeyCreator</a>
            
            base class is used instead of the 
            <a class="ulink" href="../../java/com/sleepycat/bind/serial/SerialSerialKeyCreator.html" target="_top">SerialSerialKeyCreator</a>
            
            base class.
        </p>
          </li>
          <li>
            <p>
            For all key input and output parameters, the 
            <a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleInput.html" target="_top">TupleInput</a>
            
            and 
            <a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleOutput.html" target="_top">TupleOutput</a>
            
            classes are used instead of 
            <a class="ulink" href="http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Object.html" target="_top">Object</a>
            
            (representing a deserialized object).
        </p>
          </li>
          <li>
            <p>
            Instead of returning a key output object, these methods call
            tuple write methods such as 
            <a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleOutput.html#writeString(java.lang.String)" target="_top">TupleOutput.writeString</a>.
        </p>
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      <p>
    In addition to writing key tuples, the
	<code class="classname">ShipmentByPartKeyCreator</code> and
	<code class="classname">ShipmentBySupplierKeyCreator</code> classes also read the key tuple
	of the primary key. This is because they extract the index key from
	fields in the Shipment's primary key. Instead of calling getter
	methods on the <code class="classname">ShipmentKey</code> object, as in prior examples,
	these methods call 
    <a class="ulink" href="../../java/com/sleepycat/bind/tuple/TupleInput.html#readString()" target="_top">TupleInput.readString</a>.
	The <code class="classname">ShipmentKey</code> consists of two string fields that are read
	in sequence.
</p>
      <p>
    The modified key creators are shown below:
	<code class="classname">SupplierByCityKeyCreator</code>, 
    <code class="classname">ShipmentByPartKeyCreator</code>
	and <code class="classname">ShipmentBySupplierKeyCreator</code>.
</p>
      <a id="tuple_SupplierByCityKeyCreator"></a>
      <pre class="programlisting"><strong class="userinput"><code>import com.sleepycat.bind.serial.TupleSerialKeyCreator;
import com.sleepycat.bind.tuple.TupleInput;
import com.sleepycat.bind.tuple.TupleOutput;
...</code></strong>
public class SampleDatabase
{
    ...
    private static class SupplierByCityKeyCreator
<strong class="userinput"><code>        extends TupleSerialKeyCreator</code></strong>
    {
        private SupplierByCityKeyCreator(ClassCatalog catalog,
                                         <strong class="userinput"><code>Class valueClass</code></strong>)
        {
            super(catalog, valueClass);
        }

<strong class="userinput"><code>        public boolean createSecondaryKey(TupleInput primaryKeyInput,
                                          Object valueInput,
                                          TupleOutput indexKeyOutput)
        {
            SupplierData supplierData = (SupplierData) valueInput;
            String city = supplierData.getCity();
            if (city != null) {
                indexKeyOutput.writeString(supplierData.getCity());
                return true;
            } else {
                return false;
            }
        }</code></strong>
    }

    private static class ShipmentByPartKeyCreator
        <strong class="userinput"><code>extends TupleSerialKeyCreator</code></strong>
    {
        private ShipmentByPartKeyCreator(ClassCatalog catalog,
                                         <strong class="userinput"><code>Class valueClass</code></strong>)
        {
            super(catalog, valueClass);
        }

        <strong class="userinput"><code>public boolean createSecondaryKey(TupleInput primaryKeyInput,
                                          Object valueInput,
                                          TupleOutput indexKeyOutput)
        {
            String partNumber = primaryKeyInput.readString();
            // don't bother reading the supplierNumber
            indexKeyOutput.writeString(partNumber);
            return true;
        }</code></strong>
    }

    private static class ShipmentBySupplierKeyCreator
        <strong class="userinput"><code>extends TupleSerialKeyCreator</code></strong>
    {
        private ShipmentBySupplierKeyCreator(ClassCatalog catalog,
                                             <strong class="userinput"><code>Class valueClass</code></strong>)
        {
            super(catalog, valueClass);
        }

        <strong class="userinput"><code>public boolean createSecondaryKey(TupleInput primaryKeyInput,
                                          Object valueInput,
                                          TupleOutput indexKeyOutput)
        {
            primaryKeyInput.readString(); // skip the partNumber
            String supplierNumber = primaryKeyInput.readString();
            indexKeyOutput.writeString(supplierNumber);
            return true;
        }</code></strong>
    }
    ...
}
	</pre>
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